Ground beetles respond to grazing at assemblage level, rather than species-specifically: The case of Cretan shrublands

Abstract

Phrygana, maquis and subalpine shrublands are the most typical ecosystem types on the island of Crete. However, these formations are mostly mismanaged and poorly studied in terms of their fauna and the effect of long term land-use. We studied the impact of goat and sheep grazing on the diversity patterns of carabid beetles at sites in relation to possible habitat uniqueness and geographic zonation. In total, 19,322 individuals belonging to 42 Carabidae species were identified. The composition of site assemblages was mainly determined by altitude. The six Cretan endemic species collected were widely distributed on the island and most of them were dominant. Species richness and equitability were significantly lower at overgrazed sites compared to areas with low grazing intensity. The diversity patterns of carabids were influenced by the level of grazing in each study area. As species richness and diversity were maximal under moderate/relatively high levels of grazing (hump-shaped pattern), our results support the intermediate disturbance hypothesis. Low tolerance of carabid taxa to intensive grazing was also ascertained through the significantly high values of temporal beta diversity at overgrazed sites, independent of local species richness. We conclude that Carabidae are good indicators of grazing pressure in Crete at assemblage level, rather than species-specifically. To maintain diversity and enhance niche space of invertebrate fauna, the spatiotemporal discontinuity of grazing is essential.